How do I search for a string with a partial portion of the string?

Can someone help explain why "partial" search doesn't work for me? It's an ASA syslog... when I search for a full syslog event "%ASA-4-713903" it finds it, when i search "%ASA-4-" the "%ASA-4-713903" is among the results, but when I search ""%ASA-4-71390" it finds nothing. Thanks!